Add missing import

Author: mihaimaruseac

tensorflow/python/ops/sparse_ops_test.py

@@ -24,6 +24,7 @@
 from tensorflow.python.eager import context
 from tensorflow.python.framework import constant_op
 from tensorflow.python.framework import dtypes
+from tensorflow.python.framework import errors
 from tensorflow.python.framework import sparse_tensor
 from tensorflow.python.framework import test_util
 # Need array_grad to register gradient for Identity.